1. Field of the Invention
The preset invention relates generally to a multimedia transmission system, and more particularly, to a method and apparatus for transmitting and receiving service discovery information in a multimedia transmission system, and a file structure for the same.
2. Description of the Related Art
ISO/IEC 14496-12 has proposed an International Organization for Standardization (ISO) base file format as a standard file format to be used for multimedia services. Having a flexible and extensible file structure, the ISO base file format is the basis of various multimedia file formats. The ISO base file format is designed to have an object-oriented structure so as to include various types of media resources and metadata, as a standardized file structure for packaging media resources and metadata. For example, the Joint Photographic Experts Group (JPEG) 2000, and 3rd Generation Partnership Project (3GPP) file formats are made based on the ISO base file format, and the Moving Picture Experts Group (MPEG)-4 file format is also an extension of the ISO base file format.
FIG. 1 is a diagram illustrating the general format of an ISO base file.
The information and functions necessary for playing a plurality of media contents together are created in the form of an object-based box. In the embodiment illustrated in FIG. 1, an ISO base file 101 includes a movie box ‘moov box’ 103 and a media data box ‘mdat box’ 105. While the media data box 105 stores media data (or a media stream) such as video and audio, the movie box 103 stores temporal and spatial position information and codec information for the media data stored in the media data box 105.
More specifically, the movie box 103 includes information about how to configure media data such as video, audio, texts and images, in a single scene. In the movie box 103, tracks ‘trak’ 107, 109, and 111 include basic information and playback information of their associated media data.
The track 107 includes information about audio data, the track 109 includes information about video data, and the track 111 includes information for a streaming service. For example, if the media data is audio data, the track 107 may include encoding information for audio and information about the time required in playing the audio.
A structure of the ISO base file 101 includes consecutive objects, some of which may include other objects. In the format of the ISO base file 101, the consecutive objects constitute one presentation metadata box (or the movie box 103). The movie box 103 has a dependent box defined as a container box having metadata for presentation. The media data box 105 is defined as a box having actual media data for the presentation, and the tracks 107, 109, and 111 are defined as a set of samples that are time-consecutive in the ISO base file 101. In case of multimedia data, the tracks 107 and 109 correspond to consecutive image samples or consecutive audio samples, and the hint track 111 corresponds to information about a streaming channel.
A multimedia transmission system using the above file format structure requires a method and apparatus for performing service discovery so that a client may find or select appropriate files to play.